Formation of phosphatidylethanol and ethylglucuronide after low to moderate alcohol consumption in volunteers with a previous three-week alcohol abstinence

The effect of incidental ethanol exposures on the formation of blood phosphatidylethanol

Blood phosphatidylethanol (PEth), a metabolite of ethanol, is emerging as a direct biomarker of choice for characterizing ethanol consumption in clinical, research, and forensic contexts. An accumulating body of evidence, and a recent international consensus conference, supports a cutoff of 20 μg/L of PEth (16:0/18:1) to distinguish abstinence from beverage ethanol consumption. There is a dearth of research, however, on whether exposures to nonbeverage ethanol sources are sufficient to produce PEth concentrations that exceed this cutoff. To explore this possibility, we recruited 30 participants, who indicated past-90-day abstinence from beverage alcohol, to characterize their past-30-day nonbeverage ethanol exposures (including source, frequency, and intensity of exposures) and to undergo PEth testing. Two of the 30 participants (6.7%) produced PEth concentrations ≥20 μg/L. One of these participants (PEth = 26 μg/L) reported multiple ethanol exposure sources, including near-daily intensive exposures to ethanol vapor. The other participant (PEth = 49 μg/L) reported only once-daily use of an ethanol-containing mouthwash; the veracity of his abstinence claim is refuted. The results of this study support a rebuttable presumption that PEth ≥20 μg/L is indicative of beverage ethanol consumption. They suggest, however, that intensive, incidental alcohol exposures have the potential, under unusual circumstances, to result in PEth concentrations that modestly exceed this threshold.

Monitoring of phosphatidylethanol in dried blood spots and of ethyl glucuronide in hair over 6 months of alcohol consumption

The aim of this study was to monitor seven phosphatidylethanol (PEth) homologues in dried blood spots (DBS) and ethyl glucuronide in hair (EtGH) over a 6-month period of drinking while documenting the daily drinks (amount and type) of alcohol via app. A total of 23 volunteers (12 males and 11 females) aged 19-54 years were enrolled. At four-weekly intervals, capillary blood to create DBS and after 3 and 6 months, respectively, a strand of hair (proximal, 3 cm) was collected. Analyses of EtGH and PEth homologues were performed using liquid chromatography-tandem mass spectrometry. All participants consumed alcohol during the 6 months. Only one participant tested negative for both PEth and EtGH. Eight participants had PEth 16:0/18:1 concentrations between 20 and <210 ng/mL (mean: 45.6 ng/mL) but EtGH concentrations below 5 pg/mg. PEth 16:0/18:1 concentrations between 20 and <210 ng/mL and EtGH concentrations between 5 and <30 pg/mg were assigned to eight subjects, uniformly matching them in the category of socially accepted drinking behavior. Four test subjects exceeded the cutoff for social drinking behavior in both PEth 16:0/18:1 (mean: 528 ng/mL) and EtGH (mean: 84.5 pg/mg). Two participants exceeded the threshold for PEth 16:0/18:1 of 210 ng/mL in blood but remained below 30 pg EtG/mg hair. PEth showed a higher detection rate for alcohol consumption than EtGH did. Moreover, PEth concentrations reacted quickly to changes in drinking behavior, whereas EtGH concentrations remained similar over time.

Storage stability of phosphatidylethanol homologues in whole blood and dried blood spots of nonalcoholics at different temperatures over 60 days

Phosphatidylethanol (PEth) has recently become a popular direct alcohol marker for evaluating drinking behavior. This study aimed at gaining further information on the long-term stability of five PEth homologues (16:0/18:1, 16:0/18:2, 16:0/20:4, 18:0/18:1, 18:0/18:2) in whole blood (WB) and dried blood spots (DBS) stored at -80°C, 4°C, and room temperature (18°C) over a period of 60 days. Venous blood was taken from 10 volunteers (five females and five males, aged 21-40 years) with a moderate drinking behavior and a negative breath alcohol test at the time of collection. 100 μL aliquots of WB were prepared in addition to 20 μL DBS samples. The initial PEth concentrations were determined on the day of the blood collection. On days 1, 3, 5, 7, 11, 17, 40, and 60, DBS were analyzed in triplicate by means of LC-MS/MS. On these days, WB aliquots having been stored until that time were used to create further DBS in triplicate, which were subsequently stored at 18°C and analyzed in a single batch after day 60. All homologues, except PEth 16:0/20:4, were stable at -80°C in DBS and WB for 60 days. The initial PEth 16:0/18:1 concentrations remained stable in both DBS and WB in all but one volunteer's specimen at 4 and 18°C. Apart from this exception, simultaneously detected PEth homologues 16:0/18:2, 18:0/18:1, and 18:0/18:2 remained stable over at least 40 days in DBS. Nevertheless, the storage time between sample collection and analysis should be kept as short as possible if an ethanol-free sample cannot be ensured.

The alcohol biomarker phosphatidylethanol (PEth) - test performance and experiences from routine analysis and external quality assessment

Phosphatidylethanol (PEth) are membrane molecules formed from phosphatidylcholine and ethanol through transphosphatidylation catalyzed by phospholipase D. Measurement of the main PEth form 16:0/18:1 is used as a specific and sensitive alcohol biomarker, since its formation requires ethanol, it accumulates in the blood upon repeated ethanol exposure, and it is only slowly eliminated during abstinence. PEth formation correlates with alcohol intake at the population level, albeit with considerable inter-individual variation as for the half-life during withdrawal. Over the past decade, the use of PEth has increased significantly and the applications have broadened. In Sweden, routine decision limits and the interpretation of test results for PEth were harmonized in 2013, using < 0.05 µmol/L (∼35 µg/L) as the recommended lower reporting limit and values > 0.30 µmol/L (∼210 µg/L) to indicate regular high alcohol intake. Routine test results show a large variation with about half being < 0.05 µmol/L and some even exceeding 10 µmol/L. In 2013, an external quality assessment (EQA) scheme for PEth 16:0/18:1 measurement in whole blood was also started (Equalis, Uppsala, Sweden), presently involving 56 laboratories from 13 countries. The agreement of PEth results between the laboratories has gradually improved to a CV < 15%. The current clinical and scientific information suggests that PEth values below the lower reporting limit (typically ∼0.03-0.05 µmol/L, or ∼20-35 µg/L) indicates sobriety or only low or occasional alcohol consumption, while regular high alcohol intake at levels corresponding to harmful drinking is required in most cases to reach PEth values > 0.30 µmol/L.